Lock-stitch sewing machine



p 1944. T. A. KESTELL LOCKSTITCH SEWING MACHINE 3 ShetS-Sheet 1 v Filed Aug. 12, 1942 Sept. 26, 1944. T. A. K ESTELL LOCKSTITCH SEWING MACHINE Filed Aug. 12, 1942 3 Sheets-Sheet 2 Sept. 26, 1944. T. A. KESTELL 2,353,350

LOCKSTI'ICH SEWING MACHINE Filed Aug. 12, 1942 3 Sheets-Sheet 3 020406aso100120140zso1aozmzzomzaozaaaooazowaa y- A I MAIN TAKE-UP 0 AUXILARY TAKE-UP LOOP TAKER c a (2 /JK/ A I B THREAD D MEASURE "I'OPI'HR'D E LOCK v BOTTOM F AH THREAD LocK E .6 //vi//v m PatentedSept. 26, 1944 LOCK-STITCH SEWING MACHINE Thomas Aubrey Kestell, Leicester, England, assignor to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application August 12, 1942, Serial No. 454,565 In Great Britain September 19, 1941 '1 Claims.

The present invention relates to sewing machines and particularly to an improved construction and operation of lockstitch shoe sole sewing machines of the McKay type adapted for sewing a sole to a shoe bottom by a seam passing through the sole to the inside of the shoe.

The invention is hereinafter described as embodied in a lockstitch shoe sole sewing machine which is similar to the machine described in an applicationof Gouldbourn and the present inventor which resulted in United States Letters Patent No. 2,331,118, granted October 5, 1943, comprising a hooked needle and an awl movable together in the direction of work feed and spaced apart one stitch length throughout the working cycle of the machine.

One of the various objects of the present invention is to avoid or reduce a tendency towards undesirable stretching or breaking of the needle thread in a lockstitch shoe sole sewing machine or other lockstitch sewing machine during setting of the stitches in the work.

In the machine described in said application, each stitch is set by the action of a loop taker or shuttle casing which acts to pass a loop of needle thread over a supply of locking thread and a take-up device, while a needle thread lock of the machine is closed and gripping the thread before each needle loop is so passed over the supply of shuttle or locking thread within the casing. The needle thread lock is opened immediately the stitch is set to allow an accumulation of needle thread, provided in part by the takeup and in part by a thread measuring device of the machine, to be drawn upon by the shuttle casing as it is passing the loop of needle thread around the shuttle thread supply. With this arrangement, the needle thread is tensioned during the stitch setting by the action of the shuttle casing and take-upuntil the needle thread lock is opened. The time in the machine cycle, in relation to the movement of the shuttle casing and take-up, at which the thread lock opens determines the depth in the work of the interlocking needle and shuttle threads and the tightness of the stitches.

It has been found that with this arrangement there is occasionally some tendency for the needle thread to be unduly stretched, and in some rare instances even broken, owing apparently to a somewhat sudden strain being applied to the thread by the shuttle casing and take-up before the thread lock opens.

In the illustrative machine hereinafter described, each stitch is set by the action of the loop taker or shuttle casing'and the take-up while the needle thread lock is closed but the thread lock is not opened until the loop of needle thread is in such a position that it may readily be pulled from the loop taker or shuttle casing towards the work by the take-up. The shuttle casing and take-up in the illustrative machine are caused to exert a gradually increasing strain on the thread until the stitch is set and then gradually to reduce the tension on the thread and the take-up is caused to supply suflicient thread for the shuttle casirm readily to pass the loop ofneedle thread around the shuttle thread. In this manner, sudden strains on the needle thread and consequent undesired stretching or breakage thereof are avoided or reduced.

In certain of its aspects, the present invention is not limited in its application to a McKay type sole sewing machine or to a machine in which a needle thread measuring device separate from the take-up is employed but the invention is useful with any sewing machine having a thread lock against which each stitch is set while a needle loop is passing over a loop taker or shuttle casing, an accumulation of slack thread being provided at the supply side of the thread lock for each stitch and suitable mechanism for actuating the machine being arranged to reduce substantially the tension on the needle thread while the needle loop remains on the loop taker before the thread lock is opened. There will now be given by way of example, but not of limitation, a description of the illustrative machine aforementioned, taken in connection with the accompanying drawings, from which the above and others of the various objects and the several features of the present invention will become clear.

In the drawings, Fig. 1 is a fragmentary view in front elevation, and partly in section, of a portion including the needle, awl, work supporting horn and shuttle of a shoe sewing machine embodying the present invention: Fig. 2 is a sectional view in'elevation of the base portion of the work entering and supporting horn and its actuating mechanism for the machine of Fig. 1; Fig. 3 is a detail and somewhat diagrammatic view of the shuttle, take-ups, thread locks and pull-ofi devices of the machine, together with a portion of a shoe being operated upon, showing the parts in positions assumed during a sewing cycle after each needle thread loop has been drawn through the work and applied to the beak of the shuttle: Fig. 4 is a similar view illustratin the parts at a time in the sewing cycle when the previously formed stitch is being set; Fig. 5 is a 2 a,sos,aeo

similar view of the same parts Just before a point in the sewing cycle is reached where the needle thread loop may .be pulled readily from the.

shuttle by the take-ups: and Fig. 61s a time chart indicating the motions of the parts illustrated in I'igs. 3 to 5, inclusive.

The illustrative machine is, except as will hereinafter appear, similar in construction and operation to the machine described in the appli-.

cation for patent above identified and like that machine comprises a curved hook needle 2, an a'wl 4, a rotatable work entering and supporting horn indicated at i in Figs- 1 and 2, a needle threading whirl I at the tip of the horn, a presser foot l,'a loop taker or shuttle l I having acasing containing a supply of locking thread, a main take-up l2, an auxiliary take-up l4, a thread lifter it, top and bottom thread looks it and 2|,

- up, hereinafter referred to by the term take-up" alone, while the top thread lock I8 is closed, which are caused to exert a g adually increasing strain on the needle thread (Fig. 8) to pull the inter locking portions of the needle and shuttle threads of the preceding stitch into the work to set the stitch (Fig. 4) and are then caused gradually to reduce the strain on the needle thread. The takeup then supplies suillcient needle thread to the shuttle casing to allow the latter readily to pass the loop of needle thread over the shuttle thread (Fig. 5). In the illustrative machine, the needle thread measuring mechanism only draws from the needle thread supply sufficient thread for each stitch, providing an accumulation of slack thread on the supply side of the top lock, and this accumulation of thread is drawn upon by the take-up as it is pulling the loop of needle thread which has passed over the supply of shuttle thread in the thread case down towards the work.

. The operation and relative timing of the main take-up l2, top and bottom thread locks II and ll, thread measurer 22 and shuttle casing I I of the illustrative machine will now-be described. With reference to the accompanying timing chart of Fig. 6; assuming the machine to be in operation to sew a seam and the work feeding and stitch forming devices to have reached once more the positions which they occupied when the machine came to rest, the main take-up I! (see line A on chart) willhavermentoaiveupthreadtothe needle and will continue to riseduring about the Y I first 30 of rotation of a main sewing crank shaft connected with the shaft 24 (Fig. 2). The takeup then moves downwardly somewhat during about the next 45of rotation of the crank shaft and dwells in its lowered position during about g a further of rotation of the crank shaft. The

"again and ccntinues'to rise imtii the end of the I cycle.

The shuttle casing ll (seeline B on chart) in the illustrative machine makes a single-revolu- 5 tion' during each cycle of the machine and its beak engages theloop of needle thread drawn up I by the needle and spread apart by the thread lifter i. when the crank shaft has rotated through about 40 (see Fla. 3 and point a line B of Fig. 6)

10 from its starting position. The beak on the shuttle casing is rising at this time andthe tip of its beak is on a radial line extending from the center of the shuttle casing downwardly and to the right from the shuttle casing axis at an angle is of about 40"- to the'horimntal. When the shuttle casing and the take-up are exerting a maximum tension on the needle thread to set the stitch, the crank shaft has rotated through about 100' (see Fig. 4 and point b line B of Fig. 6) from its startg ing position and the tip of the shuttle beak is on a radial line extending from the center of the shuttle casing upwardly and to the right from the axis of the shuttle casing at an angle of about 10 to the horizontal. When the take-up'has reached its-highest position, i. e. when the crank shaft has rotated through about 150 (see Fig. 5 and point 0 line B of Fig. 6) from its starting position, the point of the beak of the shuttle casing is positioned about 10. at the left of the top of the shuttle casing and as the take-up descends and shuttle casing continues to rotate, the loop of needle thread is drawn down from the beak towards the work by the take-up. The needle thread is gradually strained and the strain gradu- 5 ally released by the take-up and shuttle beak during the stitch setting while the crank shaft rotates from about 70 from its starting position to about 130 from its starting position.

The auxiliary take-up it in the illustrative machine operates to pull the loop of needle thread into the hook of the needle and to control the needle thread while the needle is rising, in a similar manner to the auxiliary take-up described in the application referred to. In the illustrative machine, the auxiliary take-up it, which is staticnary while the stitch is being set (Fig. 4), ls given a movement from the position of Figs. 4 and 5' in a direction towards the position of Fig. 3 to assist the main take-up in pulling the needle 100p away from the shuttle casing which occurs 5 next cycle of the machine.

The movements of the auxiliary take-up are indicated by the dot-and-dash lines C on the chart and have pulled the needle thread into the hook of the needle as the needle is rising in the stopping position of the machine. The auxiliary take-up continues to control the thread as the needle is rising until the crank shafthas rotated through about from its starting position. The auxiliary take-up then remains stationary until the crank shaft has rotated through about 230 from its starting position when the auxiliary take-up commences to assist the take-up in pulling the needle loop away from the shuttle casing. This movement of the auxiliary take-up con-' 1 tinues until the crank shaft has rotated through about 290' from its starting position. The auxiliary take-up is then caused to pull the needle loop into the hook of the needle and to control thethreadduringtherestofthecycleasthe 1a needle is rising.

. I The needle thread measurer 22 in the illustrative machine only measures oil andgives up to the take-up in each cycle of the machine sui'ilmeasurer in the starting position of the illustrative machine has measured of! some thread from thesupply and continues to measure of! thread during about the first 20 of rotation of the crank shaft from its starting position. The thread measurer then dwells during about the next of rotation of the crank shaft and then commences to release the measured-oil thread in readiness for it to be drawn upon by the takeup after the top lock has been opened. The thread releasing movement of the thread measurer continues during about the next 60 of rotation of the crank shaft. The thread measurer then dwells until the crank shaft has rotated through about 310 from its starting position when it measures oif thread from the supply until the end of the cycle.

The top lock l8 in the illustrative machine (see line E in chart) is closed in the stopping position of the machine and commences to open when the crank shaft has rotated through about 135 from its starting position. The top lock is fully opened during about'the next 30 of rotation of the crank shaft andremains fully open during about the next 55 of rotation of the crank shaft. The top lock then commences to close and is fully closed after about the next thirty degrees of rotation of the crank shaft.

fore the thread is fully released by the top thread lock with the result that if waxed thread is being used, some of the wax on the threadmay be removed by and caused to accumulate on the thread look. In the illustrative machine, however, this is avoided since the top lock is not opened until the strain on the thread has been fully relieved.

The nature and scope of the invention having been indicated. and a particular embodiment of the invention having been specifically described, what .is claimed is:

1. A lockstitch sewing machine having, in combination, stitch forming and setting devices including a hook needle, means containing a supply of locking thread, and a loop taker arranged to carry a loop of needle thread over the locking thread supply and a needle thread lock, means for providing an accumulation of slack thread on the supply side of the thread lock while the stitch is being set, and mechanism for actuating the stitch forming devices to cause the thread lock to be D 'ned only after the stitch setting islensign on the needle thread is substantially reuse 2. A lockstitch sewing machine having, in com- I bination, stitch forming and setting devices in. cluding a hook needle, means containing a supply of locking thread, and a loop taker arranged to carry a loop of needle thread over the locking thread supply and a needle thread lock, means The top lock then remains closed until the end of the cycle.

The bottom lock .20 in the illustrative machine (see line F inchart) is fully open in the stopping position of the machine and commences to close when the crank shaft has rotated through about 10 from its starting position. The bottom lock is fully closed during about the next 30 of rotation of the crank shaft and remains closed until the crank shaft has rotated through about 295 from its starting position. The bottom lock then commences to be opened and is fully opened during about the next 30 of rotation of the crank shaft and remains fully open during the remainder of the cycle.

In the illustrative machine, the presser foot 8 is not locked down on the work but is held a ainst it by a spring and is raised only during the feeding of the work, i. e., when the crank shaft has rotated through about 65 from its starting position until the crank shaft has rotated through about 125 from its starting position, the presser foot then being pressed down against the work by its spring. The shuttle beak and take-up exert a gradually increasing strain on the needle thread in pulling in the shuttle and needle threads and setting the stitch which occurs during about 30 of rotation of the crank shaft and this strain is gradually released during the next 30 of rotation of the crank shaft, the top thread lock l8 being closed at this time. In this way, the needle thread is not subjected to suddenly applied strains which might tend to cause undesirable stretching of the thread and may cause breakage thereof.

In the machine described in said application, the top lock I8 is opened after each stitch is set while the needle thread is being strained by the movement of the shuttle beak and take-up and may be pulled through the opening top lock befor providing an accumulation of slack thread on the supply. side of the thread lock while the stitch is being set, and mechanism for actuating the stitch forming devices to cause a gradually increasing strain to be imparted to the needle thread until the stitch is set and then a gradually decreasing tension before the loop of needle thread is passed over the locking thread supply and while the needle loop remains on the loop taker, and mechanism for actuating the stitch forming devices to cause the thread lock to be opened only after the tension on the needle thread is substantially reduced.

3. A lockstitch sewing machine of the McKay type having, in combination, devices for supporting the workincluding a rotatable shoe entering horn, stitch forming and setting devices including a hook needle, means containing a supply of locking thread, a loop taker arranged to set the stitch immediately preceding that being formed and to carry a loop of needle thread over the locking thread supply and a needle thread lock, and means for closing the lock to cause the loop taker to set the preceding stitch against the thread lock, and for opening the thread look after the tension on the needle thread is substantially reduced, said devices includin pull-off means for measuring needle thread from the supply actuated to provide an accumulation of slack thread on the supply side of the thread lock while each stitch is being set, and take-up means arranged to give up thread to the needle and loop taker and to pull the accumulation of needle thread past the thread look after the tension is reduced.

4. A lockstitch sewing machine of the McKay type having, in combination, devices for supporting the work including a rotatable shoe entering horn, stitch forming and setting devices including a hook needle, means containing a supply of locking thread, a loop taker arranged to set the stitch immediately preceding that being formed and to carry a loop of needle thread over the locking thread supply and a needle thread lock,

and means for closing, the lock to cause the loop taker to set the preceding stitch against the thread lock, and for opening the thread lock alter the tension on the needle thread is substantially reduced, said devices also including pull-oi! means for measuring needle thread from the supply actuated to provide an accumulation of slack thread on the supply side or the thread lock while each stitch is being set, and take-up means for giving up thread to the needle loop and loop taker and for exerting a gradually increasing strain on the thread while the needle loop is on the loop taker until the stitch is set,

and a gradual reduction in thread tension until Q the needle loop is passed about the locking thread supply and the thread lock is open to prevent substantial tension in the thread when the thread lock is opened and to draw needle thread past the lock as the take-up is pulling the loop of needle thread toward the work.

5. A lockstitch shoe sewing machine of the McKay type having, in combination, stitch forming and setting devices including a rotatable work entering horn, a hook needle, means containing a supply of-locking thread, a loop taker arranged to set the stitch immediately preceding that being formed and'to carry a loop of needle thread over the locking thread supply, a take-up arranged to give up thread to the needle and loop taker, a needle thread measuring pull-oil, a first needle thread lock between the pull-oi! and take-up, and a second needle thread lock on the supply side of the pull-oil, means for closing the first thread lock to set the preceding stitch during the loop drawing stroke of the loop taker and for opening the first lock alter the loop drawing stroke of the loop taker is completed, mechanism for open.. ing'the second look to enable thread to be drawn from the supply by the pull-o! and for closing 2,sse,eeo.

the second look when the first lock is open, and mechanism for actuating the take-up to impart a gradually increasing strain tothe needle thread until the stitch is set and then a gradually decreasing tension while the needle loop remains on the loop taker before first thread lock is opened.

6. A lockstitch shoe sewing machine having, in combination, stitch rorming and setting devices including a hook needle, means containing a sup-' ply of locking thread, a loop taker arranged to set the stitch immediately preceding that being formed. and to carry a loop of needl thread over the locking thread supply and a needle thread lock, means for providing an accumulation oi slack thread on the supply side of the thread lock, and mechanism for closing the lock to cause the loop taker to set the preceding stitch against the lock and for opening the lock to cause the take-up to draw the accumulation of slack thread past the lock after the loop of thread has been passed over the locking thread supply and is being pulled towards the work from the loop taker.

7. A lockstitch sewing machine having, in combination, stitch forming and setting devices comprising a hook needle, a p taker arranged to pass a loop oi needle thread over a supply or looking thread, a needle thread lock and a takeup acting with the 100p taker to set each stitch. and mechanism for actuating the stitch forming devices during the setting of astitch to cause a gradually increasing strain to be imparted to the needle thread until the stitch is set and then a gradually decreasing strain before the loop of needle thread is passed over the locking thread supply and while on the loop taker.

'rnoms AUBREY mm 

